Startup screens can vary by Mac model, operating system (macOS), and more. Startup is complete when you see the Finder menu bar, desktop, and Dock. If your Mac gets stuck at any screen, press and hold the power button until your Mac turns off, then disconnect all nonessential external devices. If that doesn't help, try using safe mode to identify the issue. If your Mac still doesn't finish starting up, you might need to reinstall macOS or restore from a backup.
Blank (empty) screen
It's normal for a blank screen to appear once or more during startup. Its background can be black, gray, blue, or a desktop picture. If an image doesn't appear after a few moments, make sure that your display is turned on, connected, and has its brightness turned up.
Apple logo or spinning globe
Your Mac displays an Apple logo when it finds a local startup disk, which is a startup disk built into or connected to your Mac. If it can't find one, it looks for one on your network. When using a network startup disk, your Mac displays a spinning globe instead of an Apple logo. A spinning globe also appears when starting up from macOS Recovery over the Internet. As startup continues, you should see a progress bar or , which might alternate with a blank screen several times.
System lock PIN code
Your Mac asks for a PIN code when it has been remotely locked using the Lost Mode feature of Find My Mac. Enter the four-digit or six-digit passcode to continue.